Abstract:
This data set consists of algorithm estimates of global Photosynthetically Active Radiation (PAR) reaching the surface obtained by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), in orbit on the OrbView-2 (formerly SeaStar) platform. SeaWiFS data products are processed and distributed by the Ocean Biology Processing Group (OBPG). Processing details can be found at ... http://oceancolor.gsfc.nasa.gov/DOCS/SW_proc.html

PAR is defined as the quantum energy flux from the Sun in the spectral range 400-700 nm. It is expressed in Einstein/m2/day. The PAR model uses plane-parallel theory and assumes that the effects of clouds and clear atmosphere can be de-coupled. The planetary atmosphere is therefore modeled as a clear sky atmosphere positioned above a cloud layer. This approach was shown to be valid by Dedieu et al. (1987) and Frouin and Chertock (1992). For additional information about the algorithm see http://oceancolor.gsfc.nasa.gov/DOCS/seawifs_par_wfigs.pdf

Each SeaWiFS Level-3 binned (9 km) data product consists of the accumulated data for all Level-2 products, for the specified instrument and resolution, corresponding to a period of one day, 8 days, a calendar month, a calendar year, or the cumulative mission. The data are stored in a representation of a global, equal-area grid whose grid cells, or "bins," have a resolution of 9.2x9.2km (approximately 81 km2).

Each given time binning period (Daily, 8-Day, Monthly, Monthly Climatology, Seasonal, Seasonal Climatology, Annual, Cumulative) is stored in two HDF files. These files include a main file containing all product-level metadata, and data for each bin filled for that product and time period; and a subordinate file, which contains the accumulated PAR data for all bins. Subordinate files must be read in conjunction with the associated main file.

Access Constraints
From the start of instrument operations through January 1, 1998, all SeaWiFS data is free and available to the public. Following January 1, 1998, SeaWiFS data for scientific research will ONLY be available to Authorized Users who have registered with the SeaWiFS Project. Any individual scientist who will be conducting research that employs SeaWiFS data must be a registered Authorized User. A single Authorized User cannot obtain data to be used anonymously by members of a research group; all of the members of the group must be Authorized Users.

Use Constraints
Publications of research results utilizing these data must acknowledge the SeaWiFS Project and the Ocean Biology Processing Group (OBPG) at the NASA Goddard Space Flight Center, Greenbelt, MD, USA.